You made that 52% up, but I think it could be about right. Baseball game outcomes are really hard to predict.
Last year, for example, the Guardians had the best won-loss % at 63%, then the Astros at 62%, then the Sox and Yankees at about 57%. If they all play a 10 game series--not against each other-- and win their usual amount, they all win 6 games. The length of the MLB season--162 games, which is 6 games a week for six months-- makes small differences seem bigger than they are.
That said, I also believe pitching matchups can be pretty decisive. But even aces can have off nights and non-aces rise to the occasion. In the 2013 ALCS, our ace was Lester, but it was Lackey who started vs. Verlander and won, 1-0.
I firmly believe that the unpredictability of games, pitchers, hitters, etc is one of the great strengths of baseball and MLB.